Coordination polymer nanobelts for nucleic acid detection

Targeted-Lymphoma Drug Delivery System Based on the Sgc8-c Aptamer

Aptamers are emerging as a promising new class of functional nucleic acids because they can specifically bind to any target with high affinity and be easily modified chemically with different pharmacophoric subunits for therapy. The truncated aptamer, Sgc8-c, binds to tyrosine-protein kinase-like 7 receptor, a promising cancer therapeutic target, allowing the recognition of haemato-oncological malignancies, among others. We have previously developed aptamer-drug conjugates by chemical synthesis, hybridizing Sgc8-c and dasatinib, a drug proposed for lymphoma chemotherapy. One of the best-characterised Sgc8-c-dasatinib hybrids, namely Sgc8-c-carb-da, was capable of releasing dasatinib at an endosomal-pH. Herein, we probed the therapeutic potential of this aptamer-drug conjugate. Sgc8-c-carb-da specifically inhibited murine A20 B lymphocyte growth and produced cell death, mainly by late apoptosis and necrosis. In addition, Sgc8-c-carb-da generated an arrest in cell proliferation, with a cell cycle arrest in the Sub-G1-peak. The mitochondrial potential was altered accordingly to these pathways. Moreover, using an in vitro cell-targeting assay that mimics in vivo conditions, we showed that Sgc8-c-carb-da displayed higher (2.5-fold) cytotoxic effects than dasatinib. These findings provide proof-of-concept of the therapeutic value of Sgc8-c-carb-da for lymphoma, creating new opportunities for the chemical synthesis of targeted biotherapeutics.

Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High-Sensitivity Detection of Metal Ions

Until now, no polymer nanobelt-shaped materials have been developed as electrochemical, optical, and mass sensors. In this work, we first develop polymer nanobelt-shaped membranes for fast and high-sensitivity detection of metal ions, which are fabricated by a new nanobelt-based processing method with simultaneous zein matrix cross-linking and curcumin cross-linking. Their morphologies, optimal detection pH, ion selectivity, and ion detection sensitivity are systematically analyzed. The limits of detection of electrospun curcumin-loaded zein membranes with a detection time of 0.5 h are as follows: cross-linked nanobelt-shaped membranes (0.3 mg/L) < uncross-linked nanobelt-shaped membranes (1 mg/L) ≈ cross-linked nanofibrous membranes (1 mg/L) < uncross-linked nanofibrous membranes (3 mg/L). The cross-linked nanobelt-shaped membranes are also applied to detect Fe³⁺ in drinking water and environmental water. Finally, the mechanisms of Fe³⁺ detection by these membranes are studied and discussed. The results demonstrate that the difference of limit of detection is dependent on if the curcumin sensor is cross-linked or not and the membrane nanostructures (nanobelts or nanofibers). Cross-linking produces stable sensor molecules on the surface and therefore induces low limits of detection. Compared with nanofibers, nanobelts have a higher surface-to-volume ratio and can have more sensor molecules on their surfaces and therefore have lower limits of detection. In addition, the as-prepared membranes had good membrane storage stability (at least 3 months at room temperature). All of these results suggest that cross-linked electrospun nanobelt-shaped membranes by a new nanobelt-based processing method are ideal platforms for sensing. We believe that they will attract increasing attention in scientific and engineering fields such as materials, environmental, and food science.

[12]aneN3 Modified Tetraphenylethene Molecules as High-Performance Sensing, Condensing, and Delivering Agents toward DNAs

Four [12]aneN3 modified tetraphenylethene (TPE) compounds with different numbers of polyamine units and structure configurations, namely 1, 2, 3, and 4, were designed and synthesized. All compounds showed strong aggregation-induced emission (AIE) features. Compounds 2 and 4 showed significant emission enhancement after the addition of ssDNAs and dsDNAs of different lengths as well as calf thymus DNA (ctDNA). Compounds 1 and 3 showed very poor fluorescent responses toward DNAs. Gel electrophoresis demonstrated the abilities of 1-4 to condense DNA effectively. Complete retardation of plasmid DNA can be achieved at a concentration of 25 μM (1), 8 μM (for 2 and 3) and 4 μM (4). Experiments including fluorescent contrastive titrations, scanning electron microscopy, dynamic laser scattering, EB displacement, and gel electrophoresis demonstrated that the four compounds were able to integrate with DNA through electrostatic interactions and supramolecular stacking. A vicinal configuration around TPE (2) and more triazole-[12]aneN3 recognition sites (4) evidently enhanced the sensing capability toward oligonucleotides, and the TPE unit played an important role in the plasmid DNA condensation process because of its strong binding. With the advantages of low cytotoxicity, effective DNA sensing, and DNA condensing properties, compound 4 was successfully applied as a nonviral DNA vector and fluorescent tracer for label-free gene delivery, which is the first example of a nonviral gene vector with AIE activity.

Hierarchical-Multiplex DNA Patterns Mediated by Polymer Brush Nanocone Arrays That Possess Potential Application for Specific DNA Sensing

This paper provides a facile and cost-efficient method to prepare single-strand DNA (ssDNA) nanocone arrays and hierarchical DNA patterns that were mediated by poly(2-hydroxyethyl methacrylate) (PHEMA) brush. The PHEMA brush nanocone arrays with different morphology and period were fabricated via colloidal lithography. The hierarchical structure was prepared through the combination of colloidal lithography and traditional photolithography. The DNA patterns were easily achieved via grafting the amino group modified ssDNA onto the side chain of polymer brush, and the anchored DNA maintained their reactivity. The as-prepared ssDNA nanocone arrays can be applied for target DNA sensing with the detection limit reaching 1.65 nM. Besides, with the help of introducing microfluidic ideology, the hierarchical-multiplex DNA patterns on the same substrate could be easily achieved with each kind of pattern possessing one kind of ssDNA, which are promising surfaces for the preparation of rapid, visible, and multiplex DNA sensors.

Highly selective and sensitive nucleic acid detection based on polysaccharide-functionalized silver nanoparticles

Polysaccharide-functionalized silver nanoparticles (Oc-AgNPs) with a mean diameter of 15 nm were utilized as a novel and effective fluorescence-sensing platform for nucleic acid detection. Tests on the oligonucleotide sequences associated with the human immunodeficiency virus as a model system showed that the Oc-AgNPs effectively absorbed and quenched dye-labeled single-stranded DNA through strong hydrogen bonding interactions and slight electrostatic attractive interactions. The proposed system efficiently differentiated between complementary and mismatched nucleic acid sequences with high selectivity and good reproducibility at room temperature.

Rectangular coordination polymer nanoplates: large-scale, rapid synthesis and their application as a fluorescent sensing platform for DNA detection

In this paper, we report on the large-scale, rapid synthesis of uniform rectangular coordination polymer nanoplates (RCPNs) assembled from Cu(II) and 4,4′-bipyridine for the first time. We further demonstrate that such RCPNs can be used as a very effective fluorescent sensing platform for multiple DNA detection with a detection limit as low as 30 pM and a high selectivity down to single-base mismatch. The DNA detection is accomplished by the following two steps: (1) RCPN binds dye-labeled single-stranded DNA (ssDNA) probe, which brings dye and RCPN into close proximity, leading to fluorescence quenching; (2) Specific hybridization of the probe with its target generates a double-stranded DNA (dsDNA) which detaches from RCPN, leading to fluorescence recovery. It suggests that this sensing system can well discriminate complementary and mismatched DNA sequences. The exact mechanism of fluorescence quenching involved is elucidated experimentally and its use in a human blood serum system is also demonstrated successfully.

Aptamers and their biological applications

Recently, aptamers have attracted the attention of many scientists, because they not only have all of the advantages of antibodies, but also have unique merits, such as thermal stability, low cost, and unlimited applications. In this review, we present the reasons why aptamers are known as alternatives to antibodies. Furthermore, several types of in vitro selection processes, including nitrocellulose membrane filtration, affinity chromatography, magnetic bead, and capillary electrophoresis-based selection methods, are explained in detail. We also introduce various applications of aptamers for the diagnosis of diseases and detection of small molecules. Numerous analytical techniques, such as electrochemical, colorimetric, optical, and mass-sensitive methods, can be utilized to detect targets, due to convenient modifications and the stability of aptamers. Finally, several medical and analytical applications of aptamers are presented. In summary, aptamers are promising materials for diverse areas, not just as alternatives to antibodies, but as the core components of medical and analytical equipment.

Aptasensor for ampicillin using gold nanoparticle based dual fluorescence-colorimetric methods

A gold nanoparticle based dual fluorescence-colorimetric method was developed as an aptasensor to detect ampicillin using its single-stranded DNA (ssDNA) aptamer, which was discovered by a magnetic bead-based SELEX technique. The selected aptamers, AMP4 (5'-CACGGCATGGTGGGCGTCGTG-3'), AMP17 (5'-GCGGGCGGTTGTATAGCGG-3'), and AMP18 (5'-TTAGTTGGGGTTCAGTTGG-3'), were confirmed to have high sensitivity and specificity to ampicillin (K(d), AMP7 = 9.4 nM, AMP17 = 13.4 nM, and AMP18 = 9.8 nM, respectively). The 5'-fluorescein amidite (FAM)-modified aptamer was used as a dual probe for observing fluorescence differences and color changes simultaneously. The lower limits of detection for this dual method were a 2 ng/mL by fluorescence and a 10 ng/mL by colorimetry for ampicillin in the milk as well as in distilled water. Because these detection limits were below the maximum residue limit of ampicillin, this aptasensor was sensitive enough to detect antibiotics in food products, such as milk and animal tissues. In addition, this dual aptasensor will be a more accurate method for antibiotics in food products as it concurrently uses two detection methods: fluorescence and colorimetry.

Fluorescence resonance energy transfer dye-labeled probe for fluorescence-enhanced DNA detection: an effective strategy to greatly improve discrimination ability toward single-base mismatch

In this article, we report on the first use of fluorescence resonance energy transfer (FRET) dye-labeled probe for fluorescence resonance enhanced DNA detection to greatly improve discrimination ability toward single-base mismatch using conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) as a sensing platform. The suggested FRET dye-labeled probe contains a 5-carboxyfluorescein (FAM) group at 5' end of the oligomer as a donor and a 6-carboxy-X-rhodamine (ROX) attached to a modified cytosine (C) base as an acceptor, which were separated by three bases. The general concept used in this DNA assay is based on adsorption of the FRET dye-labeled single-stranded DNA (ssDNA) probe by PN, which is accompanied by substantial fluorescence quenching and disappearance of FRET. The subsequent specific hybridization with its target forms a double-stranded DNA (dsDNA), resulting in desorption of the hybridized duplex from PN surface accompanied by reoccurrence of FRET and fluorescence recovery. It suggests that the discrimination ability of this FRET probe based system toward single-base mismatch is about 5.2 times that of the system based on single dye-labeled probe based system.

Poly(m-phenylenediamine) nanospheres and nanorods: selective synthesis and their application for multiplex nucleic acid detection

In this paper, we demonstrate for the first time that poly(m-phenylenediamine) (PMPD) nanospheres and nanorods can be selectively synthesized via chemical oxidation polymerization of m-phenylenediamine (MPD) monomers using ammonium persulfate (APS) as an oxidant at room temperature. It suggests that the pH value plays a critical role in controlling the the morphology of the nanostructures and fast polymerization rate favors the anisotropic growth of PMPD under homogeneous nucleation condition. We further demonstrate that such PMPD nanostructures can be used as an effective fluorescent sensing platform for multiplex nucleic acid detection. A detection limit as low as 50 pM and a high selectivity down to single-base mismatch could be achieved. The fluorescence quenching is attributed to photoinduced electron transfer from nitrogen atom in PMPD to excited fluorophore. Most importantly, the successful use of this sensing platform in human blood serum system is also demonstrated.